A defibrillator delivers measured amounts of electrical energy ("shocks") to a patient in a procedure called defibrillation. The energy is administered to the patient through paddles or pads which are connected to the defibrillator unit through a cable, and arranged in electrical contact with the patient's chest. Generally, a shock is delivered to the patient when a user presses two discharge buttons concurrently. The discharge buttons may be located on external paddle assemblies and/or on the defibrillator unit itself.
Defibrillator systems generally also include an integral monitor for acquiring electrocardiographic (ECG) data from the patient. The ECG data may be displayed on a display device in the defibrillator unit such as a CRT, printed by a recorder (which also may be provided in the defibrillator system), and/or used to control synchronized cardioversion. Synchronized cardioversion is a procedure in which the defibrillator shocks are synchronized with the ECG's R-wave. It is essential for synchronized cardioversion, therefore, that the monitor be operational and coupled to the defibrillator or an external ECG source provided to the defibrillator.
Various equipment failures can occur in a defibrillator system other than failures in the defibrillator per se, i.e. the patient shock delivery circuits. For example, the ECG front-end may fail so it cannot acquire ECG data. Or, signal processing hardware and/or software may fail so that even though ECG raw data is acquired, the R-wave cannot be identified in that data. Other failures may disable the CRT display capability, or perhaps affect the recorder unit. In known defibrillator systems, virtually any significant failures are detected and render the unit unusable. To provide maximum reliability in this life critical application, however, the basic defibrillator shock-delivery function should be made available if possible, not withstanding one or more of a myriad of possible failures in the defibrillator system. The need remains, therefore, for a defibrillator/monitor design that would allow defibrillation of a patient in an emergency situation even though one or more failures have occurred in the system.